Ozone and PM2.5 mortality Effects of Controlling Nitrogen Oxides Emissions in Urban Areas

Daniel Q. Tong (1), Daewon Byun (2), Nicholas Muller (3), Robert Mendelsohn(4)

(1) NOAA Air Resources Laboratory on assignment from Science and Technology Corporation, Silver Spring, MD, USA (2) NOAA Air Resources Laboratory, Silver Spring, MD, USA (3) Department of Economics, Middlebury College, Middlebury, VT, USA (4) School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA

     Abstract Number: 292
     Last modified: November 9, 2009

Abstract
Emissions of nitrogen oxides (NOx) leads to formation of tropospheric ozone (O3) and fine particulate matter (PM2.5), which have been associated with adverse health effects. This paper uses an integrated assessment model to study the health effects of controlling NOx emissions in several metropolitan areas in the United States. We find that reducing emissions leads to higher 24-hour O3 and PM2.5 exposures and thus causes higher health damages. This happens because freshly emitted NOx titrates O3 and reduces the levels of atmospheric oxidants, primarily hydroxyl and nitrate radicals. The diminishment of these oxidants, as a result of NOx control, slows down local formation of secondary aerosols in the cities. Consequently, reducing urban NOx emissions leads to higher 24-hour O3 and PM2.5 concentrations in the city and lower concentrations outside the cities. Because of the high density of urban population, this increases the overall exposures. This conclusion, however, is different if peak O3 concentrations are used to represent O3 exposures. In this case, reducing NOx emissions universally lowers O3 exposures and the overall health effects. This work highlights the importance of atmospheric chemistry in assessing health effects of air pollution.